In view of numerous factors such as higher energy prices and environmental concerns, the production of value-added gaseous products from lower-fuel-value carbonaceous feedstocks, such as petroleum coke and coal, is receiving renewed attention. The catalytic gasification of such materials to produce methane and other value-added gases is disclosed, for example, in U.S. Pat. No. 3,828,474, U.S. Pat. No. 3,998,607, U.S. Pat. No. 4,057,512, U.S. Pat. No. 4,092,125, U.S. Pat. No. 4,094,650, U.S. Pat. No. 4,204,843, U.S. Pat. No. 4,468,231, U.S. Pat. No. 4,500,323, U.S. Pat. No. 4,541,841, U.S. Pat. No. 4,551,155, U.S. Pat. No. 4,558,027, U.S. Pat. No. 4,606,105, U.S. Pat. No. 4,617,027, U.S. Pat. No. 4,609,456, U.S. Pat. No. 5,017,282, U.S. Pat. No. 5,055,181, U.S. Pat. No. 6,187,465, U.S. Pat. No. 6,790,430, U.S. Pat. No. 6,894,183, U.S. Pat. No. 6,955,695, US2003/0167961A1, US2006/0265953A1, US2007/000177A1, US2007/083072A1, US2007/0277437A1, US2009/0048476A1, US2009/0090056A1, US2009/0090055A1, US2009/0165383A1, US2009/0166588A1, US2009/0165379A1, US2009/0170968A1, US2009/0165380A1, US2009/0165381A1, US2009/0165361A1, US2009/0165382A1, US2009/0169449A1, US2009/0169448A1, US2009/0165376A1, US2009/0165384A1, US2009/0217584A1, US2009/0217585A1, US2009/0217590A1, US2009/0217586A1, US2009/0217588A1, US2009/0217589A1, US2009/0217575A1, US2009/0217587A1, US2009/0220406A1, US2009/0229182A1, US2009/0246120A1, US2009/0259080A1, US2009/0260287A1 and GB1599932.
In general, carbonaceous materials, such as coal or petroleum coke, can be converted to a plurality of gases, including value-added gases such as methane, by the gasification of the material in the presence of an alkali metal catalyst source and steam at elevated temperatures and pressures. Fine unreacted carbonaceous materials are removed from the raw gases produced by the gasifier, the gases are cooled and scrubbed in multiple processes to remove undesirable contaminants and other side-products including carbon monoxide, hydrogen, carbon dioxide, and hydrogen sulfide.
While it has been suggested to improve the gasification of coal by admixing coal with a selected catalyst, or catalysts, techniques heretofore suggested have not been entirely successful. For example, known methods of impregnating coal with catalyst include (a) spraying the coal with a solution of the catalyst and (b) soaking the coal in a solution of the catalyst. These methods of catalyst impregnation suffer the drawback of producing a coal with catalyst loading that is not highly dispersed, and thus a coal with reduced gasification efficiency.
One improvement to traditional methods of loading alkali metal catalysts onto coal, disclosed in previously incorporated US2009/0048476A1, involves a diffuse catalyst loading ion exchange process. This optimizes the dispersion and distribution of the catalyst species throughout the coal matrix, resulting in a catalyzed coal particle having a higher gasification activity. To obtain the maximum benefit, the disclosed process requires an extended soaking of the coal in an aqueous catalyst solution, and careful control over the concentration of the catalyst in the solution. The wet cake resulting from the soaking has a high water content, and typically must be drained prior to ultimate drying, resulting in a process inefficiency.
Therefore, there exists a need in the art to provide more efficient processes for the loading of catalyst onto coal feedstocks that utilize to the extent possible the benefit of diffuse catalyst ion exchange loading, while improving overall process efficiency.